Pyroelectric intrusion detection in motor vehicles

ABSTRACT

Pyroelectric detector systems may be used in vehicles for security applications, such as intrusion detection and anti-theft alarms. The pyroelectric detectors are small in size, highly reliable and consume very low power. They can be physically and electrically integrated with other vehicle components, including rear-view mirror assemblies in automobiles, without incurring additional installation costs. They can also be easily integrated into aircraft cockpits.

This application is a continuation-in-part of application Ser. No.08/720,237, filed on Sep. 26, 1996, now is abandoned and entitledAutomotive Pyroelectric Intrusion Detection.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of security systems for motorvehicles such as automobiles and aircraft, and, more specifically, tointrusion detection using pyroelectric detectors.

2. Related Background Art

Automotive theft is a serious problem in the United States and in manyother countries. Many security devices, including car alarms, ultrasonicscanners, ignition sensors, central locking systems, hands-free cellularphones, kill switches, electronic or RF keys, steering wheel locking andvehicle tracking devices are available to address this problem.

These devices can be categorized as either original equipmentmanufacturer (OEM) systems, which are built into the automobile by themanufacturer, or after-market systems, which are added to the automobilesubsequent to manufacture. In general, OEM systems are superior toafter-market systems because they can be incorporated in an OEM suppliedcomponent to reduce or eliminate additional installation costs in thevehicle assembly plant. In contrast, after-market systems can beexpensive, bulky and difficult to install. Existing OEM systems,however, are typically included only on high priced luxury cars. WhileOEM security devices are sometimes available as an option on lessexpensive vehicles, optional systems may have higher installation costs.An OEM security device that is inexpensive enough to include as standardequipment would be preferable.

Various types of OEM security devices are commercially available. Onesuch device is an ultra-sound intrusion detection system described inU.S. Pat. No. 5,424,711. In this system, ultrasound emission andreception elements are provided as a plurality of separate elementslocated at or near the internal surface of the roof of the vehicle. Morespecifically, the elements are located in the region of the pillarsbetween the front and the rear side panes.

The Clifford Electronics and Hornet auto security systems are twoexamples of commercially available after-market security systems. TheClifford systems, including the SuperNova II, the Arrow II and theConcept series, are radar based and are usually installed with the radarmodule located under the floor carpet in the center part of the vehicle.This system is available from Clifford Electronics, 20750 Lassen St.,Chatsworth, Calif. 91311. The Hornet auto-security systems, ProSeriesmodel, detects open vehicle doors and is electrically tied to the doorcircuitry. The system is available from Hornet Directed ElectronicsInc., 2560 Progress St., Vista, Calif. 92083.

The above OEM and after-market systems, however, suffer from a number ofsignificant drawbacks. In particular, due to their active nature, theyrequire a relatively large amount of power. Due to the relatively largepackage size, the mounting of the devices in the pillars, under thefloor carpet in the interior of the car, or in the doors is challenging.In some constructions, replacement in the event of malfunction isdifficult. The body structure and the trim of the vehicle must also bedesigned to adequately accommodate these parts. In the Clifford systems,the radar may not function properly when certain metalized window tintsare present. Finally, in the above described Hornet system, additionalsensors and mechanisms are required to detect intrusion into the vehiclevia other paths (i.e. open or broken windows), and water in the door maycause a malfunction due to the mechanical nature of the switches.

Intrusion detection systems may also be used in aircraft, which areoften equipped with expensive equipment and systems. Currently availableaircraft intrusion detection systems, however, are either too expensiveor require a large installation space which is not available in manytypes of aircraft. For example, U.S. Pat. Nos. 4,933,668 and 5,063,371describe aircraft security systems that include a central control unitwith several remotely placed controllers and numerous sensors. Thesesystems, however, tend to be bulky, heavy, complicated, and expensive.They consume large amounts of power, which may require the use of extrabatteries or power supplies in the aircraft. This can increase the bulkand weight further still. In addition, installation of these systems canbe very complicated and time consuming. U.S. Pat. No. 4,797,657describes another type of portable detection system for use insideaircraft with delayed arming and activation but no remote access.

Until now, no intrusion detection systems have been available for useon-board aircraft that have sufficiently low power consumption, lowweight, and do not require dedicated batteries. Similar considerationsalso apply for boats, busses, trucks, trains, and other uses.

One desirable attribute for intrusion detection systems for vehicles islow power consumption during operation. This allows the device tooperate for extended periods of time while the vehicle is not being usedwithout draining the battery. This is particularly important with carsand aircraft, which may sit unused for weeks or even months at a time.Thermal energy detection requires very little energy in comparison withactive infrared and ultrasonic devices. Thus, the sensing of thermalenergy is preferred over other means of detection. Thermal energy can bedetected with a variety of devices such as thermistors, thermopiles,bolometers, and photon detectors. However, these thermal energydetectors do not have sufficient sensitivity in the detection of thermalfluctuations. Furthermore, photon detectors (i.e. HgCdTe detectors) mustbe cooled down to liquid nitrogen temperature (negative 195° C.) andthus are impracticable for use in vehicle intrusion detection systems.

Pyroelectric intrusion detection systems have been used as motionsensors inside buildings for security and intrusion detection purposes.Pyroelectric systems are passive in nature, and they detect the presenceof an intruder in a defined area by sensing and responding to thethermal radiation of the intruder. However, pyroelectric intrusiondetecting devices for buildings tend to be expensive, bulky and requirea lot of power (e.g., several Watts). This makes them unsuitable for usein vehicles, where any intrusion system must be relatively inexpensive,compact, consume very low power, yet be reliable. Furthermore, buildingintrusion detection systems may not operate properly in a vehiclebecause of the extreme temperatures that can occur inside the vehicle.

Pyroelectric detectors have also been used inside automobiles forapplications other than intrusion detection. U.S. Pat. Nos. 5,071,160and 5,482,314 are directed to infrared systems for use with air bagdeployment or other types of safety restraint systems for protection ofpassengers in the event of a collision. These systems are designed tosense the presence, position and type of object in a seat, and provide acondition signal to the safety restraint system, such as an air bag.These systems can detect the presence and orientation of a child seat(front or rear-facing), an out-of-position occupant or other types ofoccupancy, and determine the appropriateness of deploying an air bag,thereby increasing the reliability and safety of an air bag activationsystem. More specifically, an ultrasonic acoustic sensor senses theposition of the driver, a pyroelectric sensor senses the presence of thedriver, a pressure transducer within the seat senses the approximateweight of the driver and an air bag control module triggers deploymentof the air bag.

U.S. Pat. No. 5,585,625 describes yet another arrangement for detectingthe presence, position, and type of object in a seat in vehicles. Thissystem operates by illuminating the seat with infrared radiation anddetecting an image of the seat using received radiation.

Each of these pyroelectric detector systems, however, are only used whenthe ignition of the vehicle is on. Moreover, none of these systems use apyroelectric detector to detect intrusion into a vehicle. Priorpyroelectric detection systems were not suitable for use as intrusiondetection systems in vehicles because they would consume too much power,and because they would be prone to false alarms in vehicularenvironments. In addition, none of the prior systems offer a low-powerintrusion detection system for use in vehicles which can be easilyintegrated with other components of the vehicle.

SUMMARY OF THE INVENTION

One aspect of the invention relates to a method of preventing the theftof a vehicle by detecting an entry or an attempted entry of a personinto the vehicle using a pyroelectric detector and generating an alertsignal when the entry or the attempted entry is detected.

Another aspect of the invention relates to a method of detectingintrusion into a vehicle by detecting a presence of a person in thevehicle using a pyroelectric detector and generating an alert signalwhen the presence of a person is detected.

Yet another aspect of the invention relates to an apparatus fordetecting the presence or entry of a person in a vehicle including oneor more pyroelectric detectors. The detectors are mounted inside themotor vehicle, and each of the detectors has an electricalcharacteristic that changes when the infrared radiation arriving at thedetector changes. The apparatus includes electronic circuitry responsiveto changes in the characteristics of the detectors, and generates analert signal when the characteristics indicate the entry or presence ofa person in the vehicle.

The method and apparatus of this invention provide a low cost, lowpower, compact intrusion detection system for use in vehicles includingautomobiles and aircraft. This intrusion detection system can beadvantageously used to prevent the theft of an entire vehicle. It canalso be used to prevent the theft of equipment or systems from thevehicle, such as audio equipment in cars, or avionic equipment inaircraft. The system operates by detecting an entry (or an attemptedentry) into the vehicle using a pyroelectric detector, and generating analert signal in response.

This intrusion detector system, which may be advantageously integratedwith various common automotive or avionic components, can monitor forsudden changes of the thermal profile of the vehicle interior,particularly when the vehicle is off. If desired, the detection systemof this invention can include more than one detector to scan a largerfield of view, or the field of view can be limited to specific areas inthe vehicle such as the radio or steering wheel of an automobile.

The apparatus of this invention advantageously does not require achopping system and is designed to minimize false alarms. In addition,if desirable, the detector system can be self-tuned to an optimalsensitivity depending on the ambient temperature and/or may includeremote activation capabilities, thereby overcoming some of the problemsof using pyroelectric detectors in vehicles.

Further advantages and features of the invention will become apparent tothose skilled in the art upon an examination of the following detaileddescription of preferred embodiments taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an intrusion detection system using apyroelectric detector.

FIGS. 2a, 2b and 2c depict an automotive rear view mirror assemblyincorporating a single pyroelectric detector.

FIGS. 2d depict a side view of an automotive rear view mirror assemblywith a pod-mounted detector.

FIGS. 3a, 3b and 3c depict an automotive rear view mirror assemblyincorporating two pyroelectric detectors.

FIG. 4 is a circuit diagram for a single detector system.

FIG. 5 is a circuit diagram for a dual detector system.

FIG. 6 is a circuit diagram for another dual detector system.

FIG. 7 is a block diagram of an intrusion detection system using apyroelectric detector for use in aircraft.

FIG. 8 depicts the front of a rack mounted intrusion detection systemfor use in aircraft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention pertains to a pyroelectric detector system for usein vehicles, particularly for intrusion detection and anti-theftapplications. The invention provides an inexpensive, highly reliablepyroelectric detector system which requires very low power to detectsudden changes in the thermal profile of the vehicle interior while thevehicle is not being used. Furthermore, the small size and simplecircuitry of the pyroelectric detector system allow the system to beeasily integrated with other vehicle components with little or noadditional installation costs.

Pyroelectric technology is attractive for vehicular intrusion detectionapplications because pyroelectric detectors are very small and caneasily be combined with other vehicle components. Pyroelectric devices,when compared with the other types of thermal energy detectors describedabove, yield the highest sensitivity level in the detection of thermalfluctuations. Furthermore, pyroelectric devices are broadband detectorsand do not require cooling. In addition, pyroelectric devices arecompatible with existing electrical systems and trimmings of manyvehicles, and hence require minimal wiring. Finally, pyroelectricdevices require very low power for operation, even while the vehicle isoff, thereby preventing any significant power drain from the battery.The present invention provides a low-cost and highly reliablepyroelectric detector system with low-power requirements for use invehicular applications.

In automobiles, the pyroelectric system of this invention can be easilycombined with automotive rear view mirror assemblies or other existingcomponents, thereby preventing any additional installation cost at theauto assembly plant. In aircraft, the present invention can be easilyintegrated into an instrument rack with a minimal amount of wiring.

Pyroelectric detectors are AC devices; they only detect temperaturefluctuations caused by changes in thermal signatures--a fixed thermalscene will not result in any pyroelectric signal. Hence, pyroelectricdetectors are ideal for detecting the motion of bodies with temperaturesdifferent from ambient. During an attempted entry, the opening of a dooror a window will cause a sudden change in the thermal scene which can besensed by the detector. The signal responses from the bodies or thechanging thermal scene can be in the form of either currents or voltageswhich can later be processed to obtain the desired parameters (i.e.distance or temperature of detected bodies).

A pyroelectric detector (PED) is selected so that it has sufficientsensitivity to detect the thermal changes inside a vehicle. A desirablepyroelectric device should have good detectivity, preferably greaterthan 10⁵ cm Hz/W (and most preferably greater than 10⁶ cm Hz/W), lownoise and high signal to noise ratio. Furthermore, it should be able toresolve a body at a temperature of about 37° C. moving at a frequency ofapproximately 5 Hz and at a distance of about 1-5 m. The pyroelectricdetector system should require less than one Watt of power, andpreferably less than 0.1 Watts, and most preferably less than 0.02Watts, when the vehicle is not being used. This level of powerconsumption is much lower than the level required for pyroelectricdetectors in buildings.

The location of the pyroelectric detector system is governed by severalissues. First, external events such as wind gusts caused by the openingof a vehicle door and movement of bodies at temperatures different fromthe normal thermal scene should be taken into account. Secondly, it isdesirable to maximize the monitoring of the interior area of the vehiclewith a minimum number of detectors. Third, for anti-theft purposes, thedetector should be directed towards the frontal cabin area of thevehicle. In intrusion detection systems, however, the rear part of thevehicle becomes equally important.

Typically, the human face is a desirable aiming point for the detectorsince it is generally warmer than the rest of the body and typically notclothed, and can therefore provide a large thermal signature. Thisproperty can be used to minimize the probability of false alarms byaiming the detector at those places where an intruder's face is likelyto appear (e.g., a point of entry into the cabin of the vehicle), so asto exclude spurious signals from other heat sources. This can beaccomplished easily by mounting the detector in a recessed hole.

Based on the above factors, excellent results can be obtained inautomobiles when pyroelectric detectors are located on a rear viewmirror assembly, which would be close to the face of any intruderattempting to drive away with a car. The location of the PED in the rearview mirror assembly is preferably rear-facing. In this configuration,the detector can be located, for example, anywhere in the bezel orcasing that holds the glass, looking back into the vehicle interior. Abottom facing detector may also be used, in which case the detector maybe located anywhere in the casing, looking down towards the seat cushionor dashboard area. Alternatively, the detector can be located in amodule that attaches to the mounting structure of a rear view mirrorsuch as a pod attached to the mounting arm. This arm is commonlyattached to a mirror mounting button on a vehicle's windshield, or to amirror mounting area that connects with the vehicle's header area. Inyet another alternative embodiment, the detector may be located behindthe glass of the mirror itself.

FIGS. 2a, 2b and 2c depict the top, side, and front view of a PEDmounted in a rear view mirror assembly. The detector 31 is mounted inthe bezel section 32 of the mirror assembly 30, so that it will face theback of the vehicle when the mirror is installed.

In an alternative embodiment of mounting on a rear view mirror assembly,the rear view mirror assembly includes a pod within which the detectoris mounted. FIG. 2d is a side view of this embodiment, which includes apod 41 in which the pyroelectric detector 42 and the associatedelectronic circuitry 43 are housed. Preferably, the pod 41 is attachedto the mirror mount 49, which attaches to the a mirror mounting button48 affixed to the windshield 47. The detectors in this embodiment may beaimed as described above, except in this case, movement of the mirror 45itself would not change the aim of the detectors. In other alternativeembodiments, the pod could be attached, for example, to a support arm orthe mirror housing. Alternatively, the detector could be mounted on orwithin a support arm.

FIGS. 3a, 3b and 3c depict the top, side, and front view of a dualdetector system using two pyroelectric detectors mounted in a rear viewmirror assembly. The detectors 35 and 36 are mounted in the bezelsection 32 of the mirror assembly 30, so that the detectors 35 and 36will face toward the driver and passenger seats when the mirror isinstalled. Alternatively, the two detectors may be placed in a pod (notshown), similar to the pod for the single detector embodiment. Asdescribed above, the detectors are preferably aimed at places where anintruder's face is likely to appear. By using two detectors with narrowfields of view, each detector can be aimed at one of these places,further reducing the probability of a false alarm, while still providingintrusion detection for both sides of the car.

In the practice of the method of this invention the detector can belocated in any assembly or at any point in the interior of the vehicle,although location in the mirror assembly is most preferred. For example,the detector can also be located anywhere in the front or back pillars.For anti-theft purposes, it can be located in any of the pillars of thevehicle such as one of the front pillars. However, if the detector islocated on the driver-side front pillar, care should be taken such thatthe steering wheel does not obstruct the detector's field-of-view.Larger vehicles such as vans or buses may require an additional detectorin the rear pillar to monitor the rear of the vehicle below the seatheight.

Another alternative location for the detectors is in a window assembly,including, for example, mounting the detectors in the window trim. Thisposition is particularly advantageous when encapsulated windows areused, including automotive backlites (i.e., rear windows). Withencapsulated windows, the window and the edge trim are encapsulatedusing a process such as extrusion, injection molding, or reactioninjection molding. Typical materials for such encapsulation arethermoplastic olefins, plasticized polyvinyl chloride, thermoplasticpolyurethane, ethylene propylene diene monomer, and two componenturethane systems. When encapsulated windows are used, the PED may beincorporated into the window trim during the encapsulation process.These detectors could provide enhanced coverage for large vehicles, lowpower consumption, and attractive aesthetics. The window mounteddetectors could be integrated with other sensors in the vehicle, orcould be the only sensors in the vehicle. This arrangement can eliminatethe need for adding conductive patterns to the windows for detectingwindow glass breakage. Alternatively, the detectors and the associatedcircuitry can be adhered to the window itself, preferably housed in anappropriate housing.

In automobiles, the detector may also be located in the center of thesteering wheel, close to the horn in the spokes of the wheel or in thetop center of the wheel. The detector may also be positioned in theheadliner, grab-bar, console, or domelight, or anywhere on the back orfront of one or both visors. It may also be located on the dashboard,preferably towards the top section and rear-facing such that a largerarea of the vehicle is covered. The detector may be located in theclock, the radio, the HVAC control panel or other accessories mounted onthe dashboard, again offering the luxury of easy integration withoutadditional assembly cost. Positioning the detector on the sunroof offersan attractive option for monitoring the entire interior of the vehicle.The integration of the detector with existing components offers theadvantage of added functionality and value without the burden of addedassembly cost in automotive plants. Finally, the detector may be locatedin places where the intruder is more likely to hide such as therear-seating area, trunk or underneath the vehicle.

In the case of aircraft, it is preferable if the entire system fits in astandard instrument aircraft rack (i.e., 6.5" wide by 1" high) commonlyused for the installation of different electronic systems. This rack canbe installed next to other instrument panels inside the cockpit. Asdepicted in FIG. 8, the detectors 162 may be included on the front panelof the rack 160. The total weight of the system should preferably bekept lower than 10 lbs, but most preferably lower than 2 lbs.

Instead of mounting the pyroelectric sensors on the front panel of therack mounted instrument, they may be mounted on a remotely locateddetector module. When space is at a premium, such as on aircraftdashboards, this module can be made relatively small, (e.g., on theorder of one or two square inches). This detector module may beconnected to the rack mounted unit via appropriate cabling.

The best location for the detector module is along the sight of theintruder, which would include the panel dashboard, windows, upperconsoles, doors and other points of entry in aircraft. Since the moduleis small, it can be positioned in any of the above locations andconnected to the instrument rack using appropriate cabling.Cockpit-mounted detectors may be replaced with detectors located inother areas of the aircraft, such as passenger compartments, cargo holdsand aircraft exteriors. A number of detectors located at different partsof the aircraft may also be used, and optionally integrated into asingle system.

FIG. 1 shows a block diagram of a pyroelectric system. The systemincludes a pyroelectric detector 10, a band-pass filter 11, an amplifier12, a comparator 13, a single event trigger 14, an alarm buzzer 15, apair of transceivers 16, 18, and a triggered data storage unit 17. Theband-pass filter 11 allows only certain frequencies (typically 0.5-10Hz) to pass through the amplifier unit. Therefore, frequencies lowerthan 0.5 Hz, which correspond to slow events or motion such as airconvection or changes in the interior ambient temperature will not bedetected. Other suitable pass bands include 1-5 Hz, and 0.1-10 Hz. Usinga narrower pass band decreases the probability of a false alarm, but canalso increase the probability of not detecting a real intrusion. Forexample, a pass band of 0.01-100 Hz would work, but would be moresusceptible to false alarms.

Selection of the pass band overcomes one of the problems of adapting atypical house PED system to a car. Because houses are large, an intruderwould ordinarily be detected by a home PED when he is between 5 and 50feet away from a detector. The motion of an intruder at these distancesresult in low frequency signals at the PED output. In contrast, theshort distances inside a car of about 1-3 feet would result in higherfrequency signals. Meanwhile, in a car, environmental factors, such as acloud passing over the sun, can produce low frequency signals. Byfiltering out these low frequency signals, the chance of a false alarmcan be reduced. In small aircraft, a similar band pass filter may beused. This band may be opened up to include lower frequencies in largeraircraft.

The amplifier 12, which may include a preamplifier stage, amplifies thecurrent or voltage signals generated by the pyroelectric detector inresponse to external conditions. Including a preamplifier can helpreduce noise. A comparator circuit 13, having low and high thresholds,can be used to trigger the alarm. The thresholds of the comparator canbe adjusted by the user to control the sensitivity of the system todetect an intruder while avoiding spurious false alarms due tobackground thermal fluctuations such as air turbulence. The single eventtrigger 14 ensures that when the alarm 15 is turned on upon registeringan event from the comparator, it will remain on for a predeterminedtime. This single event trigger may comprise a monostable multivibrator(i.e. a "one-shot").

Each PED 10 may comprise single or multiple elements enclosed in thesame package. The package may be a standard TO-5 Transistor package,which is a popular metal can package. A PED packaged in plastic such asepoxy, polysilane or silicone may also be used. The package may includethin film elements, a thick film load resistor, and aJunction-Field-Effect Transistor (JFET) pre-amplifier. Preferably, allcomponents are hermetically sealed in the package.

When a pyroelectric detector with a single sensing element is used, thesystem can be overly sensitive to changes in ambient temperature, whichcould result in false alarms. Using PEDs with two sensing elementsarranged in a parallel opposed connection solves this problem. In thisconfiguration, equal radiation arriving at both elements will becancelled, while a defined moving radiation source that passesselectively through at least one of the elements will produce adetectable output. Similar results can be achieved when the two elementsare arranged in a series opposed connection.

FIG. 4 depicts a circuit that may be used for pyroelectric detectionusing a single detector with two parallel opposed sensing elements. Thecircuit includes the detector, which is preferably housed in a threeterminal TO-5 metal can package 51, indicated by the dashed line.Included in the TO-5 package are the pyroelectric elements 56, 57, theload resistor 58, and the impedance matching J-FET pre amplifier 52. Adetector with series opposed sensing elements may be used in place ofthe parallel opposed connection shown in FIG. 4. Alternatively, each ofthe detecting elements 56, 57 may be replaced with a pair of detectingelements connected in series.

The output from the detector is taken from the source of the J-FET 52.The source of the J-FET is connected to the TO-5 housing ground pin 54,via a resistor 55. The drain of the J-FET 52 is connected directly tothe 9 volt power supply 60. In place of the battery 60 shown, an LM7809voltage regulator (not shown) may be used to regulate the vehicle's 12volt system down to 9 volts. A polarized capacitor 59 filters thesignal, allowing only the low frequency components of the signal toreach the input of op-amp 70a. The signal is amplified by the op-amp70a, with the gain determined by the ratio of the resistors 61 and 62.The capacitors 65 and 66 also act as part of a first band-pass filter.The signal then passes through to the second amplification stage throughcapacitor 67 which also only allows AC signals to pass. This capacitoralso serves a secondary function in the low frequency end of the secondband-pass filter in conjunction with capacitor 68. The filtered signalis amplified by op-amp 70b, with the gain determined by the ratio ofresistors 63 and 64.

The filtered and amplified signal 69 is then sent to thewindow-comparator stage of the circuit 70c, 70d. The signal is routed tothe non-inverting input of the upper threshold stage 70c, and theinverting input for the lower threshold stage 70d. The voltagethresholds are set by trimming the potentiometers 71, 72. The output ofthe window-comparator stage is zero unless the signal is above or belowthe set thresholds, in which case the output is a positive voltage whichcrosses one of the diodes 73, 74 and signals an alarm. Setting thethreshold values close to the baseline results in high sensitivity butmay also result in excessive false alarms.

A significant increase in field of view can be obtained by usingmultiple detectors which may eliminate the need for optics. Each packagemay comprise multiple twin sensing element detectors, with each twinsensing element pair compensating for temperature individually. This mayallow for increased sensitivity while minimizing the thermal noiseassociated with changes in the vehicle's ambient temperature. Thisconfiguration provides benefits not found in PED based home intrusiondetection systems.

FIG. 5 depicts a circuit that uses two pyroelectric detectors 81 and 91,each of which is preferably housed in a three terminal TO-5 metal canpackage, indicated by the dashed line. Included in the TO-5 package arethe pyroelectric elements 81a and 91a, load resistors 81b and 91b, andimpedance matching J-FET pre amplifiers 81c and 91c. Preferably, thepyroelectric elements in each detector are connected in aparallel-opposed configuration, as shown in FIG. 5. However, otherconfigurations, including single element detectors and series-opposedelement pairs, may also be used. The output from each detector is takenfrom the drains of the J-FETs 82, 92. The sources of the J-FETs 83, 93are connected to the TO-5 housing ground pin 84, 94, via the resistors105. The resistors 107 are connected between each output 82, 92 and the9 volt power-supply 113. The two detectors baselines are summed viaresistors 106 and capacitors 108. An amplifying band pass filter isformed by the LM324 op-amp 112a and the resistors 110 and 112 and thecapacitors 111 and 113. As with the single detector version, theamplifier-filter can be adjusted to achieve the desired gain andfrequency characteristics. The capacitor 113 allows for amplification ofonly low frequency AC signals, while still maintaining a stable DCoperating point. Gain is set by adjusting the ratio of resistors 110 and112. The band-pass filter is set by resistor 110 and capacitor 111 (atthe low frequency end) and resistor 112 and capacitor 113 (at the highfrequency end). The signal 121 is connected to the input of thefilter-amplifier. Resistors 109 provide a bias current path as well asestablish a quiescent DC input voltage for the amplifier-filter.

The output of the amplifier-filter 119 goes to the input of the windowcomparator stage 112b, 112c. The thresholds are set by the resistortrimmers 114, 115. The outputs of the window comparators 112b, 112c aresent across equal valued resistors 116 and then on to the non-invertinginput of the final stage of the quad op-amp 112d. The op-amp 112d sumsthe two window-comparator voltages. Either op-amp 112b or op-amp 112cwill be high or both will be low. The voltage at the non-inverting inputof op-amp 112d will therefore be approximately 4.5 volts when bothsensors are outside the window, or approximately zero volts when bothsensors are inside the window. The reference voltage at the invertinginput of op-amp 112d is set at approximately 3 volts by the resistordivider formed by the resistors 117, 118. The output of op-amp 112d willtherefore go to the positive rail whenever either 112b or 112c goeshigh.

FIG. 6 is another intrusion detection circuit that uses two detectors.Initially, the incoming DC power from the vehicle is filtered by EMIfilter 250. Diode 251 protects the remaining circuitry from damagecaused by inadvertent power supply reversal, and zener diode 252protects against an overvoltage condition. Capacitor 253 filters theincoming power.

The input power is then regulated down to 9 volts, which is used topower the electronics. The regulator includes a transistor 255configured so that the voltage at the emitter will follow the voltage atthe base. This base voltage is determined by the zener diode 256, whichis supplied with operating current through the resistor 254. Because thezener voltage of the zener diode 256 is present at the base of thetransistor 255, the emitter of the transistor 255 will follow the zenervoltage. The emitter voltage at the transistor 255 is filtered by anelectrolytic capacitor 257 and a nonelectrolytic capacitor 258 (e.g., aceramic disc capacitor). Two capacitors are used to decouple both highand low frequency noise. The regulated voltage is then used to power theremaining circuitry.

The intrusion detection circuit includes two pyroelectric detectors 201and 202. The conductance of each pyroelectric detector 201 and 202changes in response to incident infrared radiation. The circuitincluding the pyroelectric detector 201 and the resistors 203 and 205produce a signal at the output of the pyroelectric detector 201 relatedto the arriving infrared radiation. Similarly, the circuit including thepyroelectric detector 202 and the resistors 204 and 205 produce a signalat the output of the pyroelectric detector 202 related to the arrivinginfrared radiation. The outputs of the two pyroelectric detectors 201and 202 are combined because they are both connected to the bottom nodeof the resistor 205.

This combined output signal is filtered by EMI filter 206. Additionalfiltering is provided by the capacitors 207 and 213 and the resistor208. The filtered signal then arrives at the non-inverting input of theoperational amplifier (op-amp) 216. Preferably, all the op-amps in thecircuit consume very low power and are included together in a single IC(integrated circuit) package. The LP2902 and LP324 op-amps arepreferred. Op-amp 216 acts in conjunction with capacitors 209 and 211,and resistors 210 and 212, to provide a first stage of amplification andband-pass filtering.

A second stage of amplification and band-pass filtering is provided bythe op-amp 224, in conjunction with the resistors 221 and 219 and thecapacitors 217 and 220. The resistors 222 and 223 provide bias for thenon-inverting input of the op-amp 224. The output of this second stageamplifier is the signal 239.

The signal 239 is then compared to a lower threshold and an upperthreshold by a set of window comparators. When the signal 239 is betweenthe two thresholds, the output transistor 236 turns off. When the signal239 is outside the two thresholds, the output transistor 236 turns on.

The lower threshold is determined by the voltage divider formed byresistors 225 and 226. If the signal 239 is lower than the lowerthreshold, the output of op-amp 227, which is used as a comparator, willgo to the positive rail. The upper threshold is determined by thevoltage divider formed by resistors 228 and 229. If the signal 239 ishigher than the upper threshold, the output of op-amp 230, which is alsoused as a comparator, will go to the positive rail.

When either of the comparator outputs 227 and 230 are driven to thepositive rail, the positive voltage will pass through one of the diodes232 and 233. This signal will then pass through resistor 235 and turn onthe output resistor 236. When the output transistor 236 is on, it sinkscurrent through the resistor 237. When neither of the comparator outputs227 and 230 are at the positive rail, no signal is passed through thediodes 232 and 233, and the transistor 236 will turn off. As a result,no current will be sinked through the resistor 237.

The following table shows one set of suitable component values for thecircuit of FIG. 6. Those skilled in the art will recognize wherealternative parts may be used.

    ______________________________________                                        reference numbers                                                                            type     value/P.N.                                            ______________________________________                                        216, 224, 227, 230                                                                           op amp   1/4 LP2902                                            201, 202       detector Hamamatsu P6592-02                                    255            transistor                                                                             2N2222                                                236            transistor                                                                             MPSA06                                                251, 232, 233  diode    RLR4004                                               252            zener    MM525245                                              256            zener    MM525239                                              253, 258, 231  capacitor                                                                              0.01 μF                                            257, 209, 213, 217                                                                           capacitor                                                                              10 μF                                              207            capacitor                                                                              220 pF                                                211, 220       capacitor                                                                              0.022 μF                                           254            resistor 390K                                                  203, 204, 208  resistor 100K                                                  205            resistor 200K                                                  210            resistor 47K                                                   212            resistor 470K                                                  222, 223       resistor 2M                                                    221, 225, 228  resistor 1M                                                    219, 235       resistor 10K                                                   229            resistor 1.5M                                                  226            resistor 680K                                                  237            resistor 50 Ω                                            250, 206       EMI filter                                                                             Panasonic                                                                     EXC-EMT103DT                                          ______________________________________                                    

For improved signal to noise ratio performance, each detector cancomprise two parallel sets of elements, with each set comprising twoseries opposed pyroelectric detecting elements. This configuration canbe used with both the single detector circuit and the dual detectorcircuit described above.

Performance of the circuit can be improved by thermally isolating thePEDs from the surface upon which they are mounted. The circuit can alsobe shielded against EMI and RFI (electromagnetic and RF interference) byenclosing either the entire circuit or the PEDs inside a Faradaic shell,by keeping the leads at the PED short, using a ground plane and bypasscapacitors, and adding ferrite beads or EMI/RFI filters at the powersupply and detector outputs. This shielding would reduce the chance ofradiation from an external source from causing a false alarm. This isparticularly important because cellular phones and remote keyless entrytransmitters are commonly used in the vicinity of vehicles, and generateRF signals that could cause interference and result in false alarms.

False alarms can also be eliminated by limiting the field-of-view to annarrow beam aimed at the points of entry. This can easily beaccomplished by mounting the PEDs in a recessed hole. This enables thebaseline of the detector to be stabilized, which in turn, narrows downthe comparator circuit window. Finally, a band pass filter can be usedto filter out unwanted signals, as described above.

If installed on the rear-view mirror assembly the detector system may beintegrated with the other functions in the rear-view mirror assembly,such as lights, electrochromic functions, compass, keyless entry, etc.In this manner, the circuitry of the detector can be built on the samecircuit board as the one used for the other functions in the rear-viewmirror assembly. Therefore, some of the elements on the board may beshared. It is further possible to design a single ASIC (ApplicationSpecific Integrated Circuit) chip that incorporates the pyroelectricsystem circuit along with the circuitry for all other functions of themirror assembly.

Typically, a human body emits radiation in the 8-14 micron wavelengthrange. This radiation is absorbed by the detector, converted to heat,and later to an electric signal. Therefore, a filter material should beinstalled between the detector and the view to block radiation in otherwavelength ranges to avoid false alarms. A lens can also be positionedbetween the detector and the view to focus the radiation onto a smallspot on the detector. The design of the lens influences the angle ofview perceived by the system. Ideally, the lens should be of a materialwhich will act as a filter that transmits radiation in the 8-14 micronwavelength range and blocks radiation in the 0.3 to 3 micron region.Filtering out visible light prevents false alarms caused by movingshadows outside the vehicle that momentarily fall on the detector. Glasswindows in automobiles and aircraft do not transmit radiation above 2-3microns. By using a detector filter window which transmits principallyin the 8-14 micron range, only radiation originating from the interiorof the vehicle, and not from the vehicle surroundings, will be detected.

The filter window materials may be made with at least one of Ge, Si,ZnS, CdS or Polyolefin (including Polypropylene, Polyethylene,Polymethylpentene, copolymers, etc.) because they transmit in the 8-14micron wavelength. Ge has better transmission properties than Si in theinfrared region but is more expensive than Si. An inexpensive plasticFresnel lens, commercially available for infrared applications, may beused. When multiple detectors are used, an individual window may be usedfor each detector.

In order to increase the field of view of the device whilesimultaneously minimizing the costs associated with additionaldetectors, a reflector may be positioned around the detector to collectthe radiation from a wider angle. Other optical configurations such as afish eye lens, a diffractive optic lens, or a combination of such lensesmay also be used. The optical elements can also be designed to allowflexibility in the orientation and the location of the detectorplacement. For example, the detector located in the interior mirrorassembly could be forward facing, but a reflector system could collectthe radiation from the desired locations of the vehicle and transmit thesame to the detector.

The filter window may comprise multiple film interference filters suchthat interference of the layers blocks unwanted wavelengths. If no otherfilters are used, it may be necessary to provide a scratch resistantwindow. Ge windows are typically coated with a layer of ZnS which isdurable and scratch-resistant.

The sensitivity as well as the direction of the pyroelectric intrusionsystem may be set by the user. The ambient temperature inside a vehicleis influenced by the time of day, environmental conditions such asoutdoor weather and the seasons, and whether the vehicle is parkedindoors or out. When the interior of the vehicle is expected to bearound 38° C. (about 98° F.), a higher sensitivity setting may bepreferable because the temperature difference between the intruder'sbody and the vehicle interior is small. In addition, the user may alsowant to aim the detector towards a particular position to enhancedetection. If the detector is connected to the rear-view mirror itself,the driver has the freedom to adjust the field-of-view of the detectorby moving the rear-view mirror. Alternatively, the detector could bemounted in a pod so that it remains stationary despite any movement ofthe mirror.

Power should be provided to the system even when the vehicle is turnedoff. Power may be provided from the vehicle battery, an auxiliarybattery, a solar cell or any other readily available power source.Optionally, a rechargeable battery can be used together with a solarcell for charging the battery.

When the vehicle is not in use, the only available power source foroperating the system is often a battery (such as a 12V lead acid batterytypically used in automobiles). In this case, minimizing powerconsumption by minimizing current draw becomes particularly important,because vehicles operating on battery power have a finite power capacity(which is typically on the order of 20 to 100 Amp-hours in automobiles).If too much current is drawn from the battery when the vehicle is notused for extended periods, the battery may not have sufficient energy tostart the engine when the vehicle is eventually used. The amount ofcurrent that will drain a battery depends on the amount of time thecurrent is being drawn. Because the amount of time between uses of avehicle may range from minutes to hours, days, or even weeks, reducingthe current drain becomes very important.

Preferably, the entire system consumes below 5.0 mA at 12 V, morepreferably below 1.5 mA, and most preferably below 0.3 mA. This level ofpower consumption does not cause any significant power drain on thevehicle battery, even when the system operates for extended periods oftime. It can be compared, for example, to Ford cars which may draw up to23 mA at 12 V when parked to keep the clock and other electronicfeatures of the vehicle running. The use of low power components, suchas the LP2902 and LP324 op-amps, helps reduce the power consumption ofthe circuit. Implementing the circuitry in an ASIC can help reduce powerconsumption even further.

The system may be turned on manually from inside the vehicle. Forexample, the detector can be activated or deactivated by punching a codeon a keypad located anywhere in the vehicle. When the system is turnedon, some delay may be needed to allow the driver to exit the vehicle andfor the system to reach equilibrium.

Alternately, the system may be turned on remotely from outside thevehicle, using a handheld unit. The handheld unit may contain one ormore pushbuttons. Remote activation allows the user to arm or disarm thesystem while outside of the field-of-view of the detector. Therefore,the delay can be reduced in remote activation systems because the systemwill not need to equilibrate itself.

Returning to FIG. 1, upon sensing the presence of an intruder, an RFalert signal will be generated by the transceiver 16 mounted in thevehicle. This RF signal is received by the handheld unit 18, whichcauses a buzzer located in the handheld unit to sound. The buzzer mayoptionally be turned off after 10 seconds to conserve power for thevehicle-mounted transceiver. By this time, a trigger will be registeredin the circuit 17. If the driver is out of range of the RF transmission,this trigger will be retransmitted to the handheld unit when the drivereventually comes within range. In this manner, the driver can be alertedto the presence of an intruder and proper safety measures can then betaken. The time lag between the alarm and the buzzer sounding depends onthe distance and location of the person from the vehicle. This time lagis typically on the order of one second or less. The handheld unit mayalso include a vibrating option, similar to most paging systems. Thehandheld unit may have a rechargeable battery that can be chargedthrough the cigarette lighter or through another mechanism.

Various alert alternatives may be used, including audible and visualalerts. In cars, this could include the flashing of headlights andinterior lights, the sounding of a horn, the locking of doors, thelocking of the ignition, irreversible power freeze, and a cellular phonecall to 911 or another user-specified number to alert the user. Variousalternate transmission methods may also be used, including transmissionusing microwaves, light (including IR), radar, acoustics and cellularphones.

Similar alert mechanisms may also be used in aircraft. But becauseaircraft and avionics systems are generally more valuable thanautomobiles, more sophisticated alert mechanisms may be desired foraircraft. These could include using a paging system to alert the user orowner of the aircraft. FIG. 7 is a block diagram of one such a system.The outputs of the pyroelectric detectors 161 are processed byappropriate electronic circuitry 153 as described above. A conventionalRemote Keyless Entry (RKE) and Alarm system 151 receives a triggersignal from the circuitry 153 when an intrusion has been detected. TheRKE/Alarm system 151 can then signal the pager 152 to page a remotereceiver. In this configuration, the owner carries a pager receiver (notshown) which will be activated by the signal from the pager 152. Thepaging system may be proprietary, or, alternatively, it may make use ofexisting paging systems. The system could even be interfaced with aglobal positioning system (GPS). In this configuration, when intrusionoccurs, the GPS equipment will be turned on and will send the vehicle'sposition to the transmitter, for transmission to the owner. A 2-wayremote communications link can also be installed between the aircraftsystem and the aircraft owner.

The intrusion system may also activate other safety or securityfeatures, such as a visible or infra-red camera located in the vehicle.The VV6850 and VV5850 CMOS image sensors from VLSI Vision Ltd. inScotland are suitable for this purpose, as are numerous other cameras.The camera can take a snapshot or a video of the vehicle interior uponalarm triggering and store the image in a memory system. At night, aninfrared or visible light may be turned on briefly to enhance thepicture quality. The image can also be transmitted and stored in thehandheld unit where it may also be viewed on a display, or transmittedto a remote receiver.

While the pyroelectric intrusion detection circuitry itself consumesvery low power, as described above, once an intrusion has been detected,power consumption may be temporarily increased to alert the owner and,optionally, to confirm the intrusion. This can be accomplished byleaving the power to the alert and confirmation circuitry off until thealert or confirmation function is needed. At that point, the circuitrycan be awakened (i.e. activated) and used to perform its intendedfunction.

Intrusion confirmation can be implemented by having the pyroelectriccircuitry activate secondary systems such as radar, ultrasonic or videocameras, and other imaging systems to confirm the intrusion. The alertsignal is only activated if the secondary system confirms the intrusion,thereby reducing the probability of false alarms.

If an intruder destroys the PED system upon entry, the destruction willbreak a circuit which will instantaneously register an alarm. Thisinformation may also be sent to the handheld unit or stored elsewhere inthe vehicle to alert the driver upon his/her return. For example, assoon as the PED is destroyed, the system could start transmittingcontinuously or at one-minute intervals. Once the user comes within thefield-of-view of the detector, the hand-held remote transceiver wouldbegin to beep or vibrate. The circuit can also be designed to check forthe electrical continuity of the detector, hence ensuring that thedetector is part of the circuit. The remote unit may also be configuredto warn the driver of a communications failure while the driver is stillat a safe distance from the vehicle.

Optionally, a solar panel that charges a rechargeable battery can beused as a power source for the pyroelectric detector system. Forexample, the forward facing surface of a mirror pod mount that isequipped with the pyroelectric detection system can contain a solar cellor panel so that light incident thereon after passage through thevehicle windshield generates electrical power to run the circuitry ofthe pyroelectric detector system. A rechargeable battery is alsoincluded as an alternate power source for use when the solar power isineffective, such as at night or when the vehicle is parked indoors.During the daytime, the solar cell or panel recharges the battery.

Optionally, the power to the circuitry of the pyroelectric detectionsystem can be switched on and off at a frequency of, for example, 0.25Hz to about 5 Hz (more preferably, 0.75 Hz to 1 Hz), so that powerconsumption over long periods is even further minimized. With thisarrangement, the pyroelectric detection system is activated in shortbursts that repeat about once a second.

Other variations and modifications of this invention will be obvious tothose skilled in this art. This invention is not limited except as setforth in the following claims.

What is claimed is:
 1. A method of ensuring reliable thermal detectionof the presence of a body having a thermal profile in a compartment of aparked motor vehicle comprising the steps of:providing a thermal energydetection system including a pyroelectric detector, said pyroelectricdetector having a first pyroelectric sensing element and a secondpyroelectric sensing element, said first and second pyroelectric sensingelements arranged in opposed connection, said thermal energy detectionsystem further comprising control circuitry responsive to electricalindicatives generated by said opposed first and second sensing elements;mounting said thermal energy detection system either in a trunkcompartment or an interior compartment of the vehicle; monitoring athermal profile of said trunk compartment or said interior compartmentof the vehicle using said thermal energy detection system when thevehicle is parked and operating under vehicle battery power; sensing achange in the thermal profile due to the presence of a moving human bodyhaving a temperature different than the thermal profile; and generatinga signal indicative of the change in the sensed thermal profile in thetrunk compartment or the interior compartment,wherein said thermalenergy detection system is responsive to frequencies of change in sensedthermal profile in a restricted frequency range, thereby reducing thechance of a false alarm situation.
 2. The method according to claim 1,wherein radiation incident on said pyroelectric detector is filtered tohave a wavelength between approximately 8 and 14 microns.
 3. The methodaccording to claim 1, wherein said thermal energy detection systemresolves movement of a body at about 37° C. moving at a distance ofwithin about 1 to 5 meters of said pyroelectric detector.
 4. The methodaccording to claim 1, wherein said thermal energy detection systemresolves movement of a body at approximately 37° C. moving at afrequency of approximately 5 Hz.
 5. The method according to claim 1,wherein the sensing step senses with a sensitivity greater thanapproximately 10⁵ cm Hz/W.
 6. The method according to claim 1, whereinthe sensing step senses with a sensitivity greater than approximately10⁶ cm Hz/W.
 7. The method according to claim 1, wherein said thermalenergy detection system has a power consumption of less than 1 Watt whenconnected to vehicle battery power and when the vehicle is in the parkedstate.
 8. The method according to claim 1, wherein said thermal energydetection system has a power consumption of less than 1 Watt whenconnected to vehicle battery power and when the vehicle is in the parkedstate.
 9. The method according to claim 1, wherein said thermal energydetection system has a power consumption of less than 0.02 Watt whenconnected to vehicle battery power and when the vehicle is in the parkedstate.
 10. The method according to claim 1, further comprising:providinga lens, said lens positioned in front of said pyroelectric detector andfocusing incident radiation onto said pyroelectric detector.
 11. Themethod according to claim 10, wherein said lens comprises a materialthat transmits radiation in approximately the 8 to 14 micron wavelengthrange.
 12. The method according to claim 11, wherein said lens blocksradiation having a wavelength of approximately 0.3 to 3 microns.
 13. Themethod of claim 10, wherein said lens comprises a material comprising atleast one of Ge, Si, ZnS, CdS and a polyolefin.
 14. The method of claim10, wherein said lens comprises a polyolefin material.
 15. The method ofclaim 10, wherein said lens comprises a material including at least oneof a polypropylene, a polyethylene and a polymethylpentene material, ora copolymer thereof.
 16. The method of claim 10, wherein said lenscomprises at least one of a fish eye lens, a diffractive optic lens, awide angle lens and a Fresnel lens.
 17. The method of claim 10, whereinsaid lens comprises a plastic lens.
 18. The method of claim 1, whereinsaid thermal energy detection system consumes a current of less thanapproximately 5.0 mA when operating under vehicle battery power.
 19. Themethod of claim 1, wherein said thermal energy detection system consumesa current of less than approximately 1.5 mA when operating under vehiclebattery power.
 20. The method of claim 1, wherein said interiorcompartment comprises a rear-seating area of the vehicle.
 21. The methodof claim 1, wherein said thermal energy detection system is provided asa module.
 22. The method of claim 1, wherein said control circuitrycomprises an application specific integrated circuit.
 23. The method ofclaim 1, wherein said opposed pyroelectric sensing elements are arrangedin a parallel opposed connection.
 24. The method of claim 1, whereinsaid opposed pyroelectric sensing elements are arranged in a seriesopposed connection.
 25. The method according to claim 1, wherein saidrestricted frequency range is between approximately 0.5 Hz and 10 Hz.26. The method of claim 1, wherein said signal generating step will notgenerate a signal for changes in the sensed thermal profile that areless than approximately 0.5 Hz.
 27. A method of ensuring reliablethermal detection of the presence of a body having a thermal profile ina compartment of a parked motor vehicle comprising the stepsof;providing a thermal energy detection system including a pyroelectricdetector, said pyroelectric detector comprising a first pyroelectricsensing element and a second pyroelectric sensing element, said firstand second pyroelectric sensing elements arranged in opposed connection,said thermal energy detection system further comprising controlcircuitry responsive to electrical indicatives generated by said opposedfirst and second sensing elements; mounting said thermal energydetection system either in a trunk compartment or an interiorcompartment of the vehicle; monitoring a thermal profile of said trunkcompartment or said interior compartment of the vehicle using saidthermal energy detection system when the vehicle is parked and operatingunder vehicle battery power; sensing a change in the thermal profile dueto the presence of a moving human body having a temperature differentthan the thermal profile; and generating a signal indicative of thechange in the sensed thermal profile in either the trunk compartment orthe interior compartment,wherein said thermal energy detection systemresolves movement of a human body at approximately 37° C. moving at adistance of approximately 1 to 5 meters of said pyroelectric detector,whereby thermal radiation emitted by said moving human body incident onat least one of said first pyroelectric sensing element and said secondpyroelectric sensing element generates an output of said thermal energydetection system indicative of presence of a human body in either thetrunk compartment or the interior compartment.
 28. The method accordingto claim 27, wherein said thermal energy detection system is responsiveto frequencies of change in sensed thermal profile in a restrictedfrequency range.
 29. The method according to claim 28, wherein saidrestricted frequency range is between approximately 0.5 Hz and 10 Hz.30. The method according to claim 27, wherein radiation incident on saidpyroelectric detector is filtered so as to having a wavelengthapproximately between 8 to 14 microns.
 31. The method according to claim27, wherein said thermal energy detection system resolves movement of abody at approximately 37° C. moving at a frequency of approximately 5Hz.
 32. The method according to claim 27, wherein the sensing stepsenses with a sensitivity greater than approximately 10⁵ cm Hz/W. 33.The method according to claim 27, wherein the sensing step senses with asensitivity greater than approximately 10⁶ cm Hz/W.
 34. The methodaccording to claim 27, wherein said thermal energy detection system hasa power consumption of less than approximately 1 Watt when connected tovehicle battery power and when the vehicle is in the parked state. 35.The method according to claim 27, wherein said thermal energy detectionsystem has a power consumption of less than approximately 0.1 Watt whenconnected to vehicle battery power and when the vehicle is in the parkedstate.
 36. The method according to claim 27, wherein said thermal energydetection system has a power consumption of less than approximately 0.02Watt when connected to vehicle battery power and when the vehicle is inthe parked state.
 37. The method according to claim 27, furthercomprising:providing a lens, said lens positioned in front of saidpyroelectric detector and focusing incident radiation onto saidpyroelectric detector.
 38. The method according to claim 37, whereinsaid lens blocks radiation having a wavelength of approximately 0.3 to 3microns.
 39. The method of claim 37, wherein said lens comprises apolyolefin material.
 40. The method of claim 37, wherein said lenscomprises a material comprising at least one of a polypropylene, apolyethylene and a polymethylpentene material, or a copolymer thereof.41. The method of claim 37, wherein said lens comprises at least one ofa fish eye lens, a diffractive optic lens, a wide angle lens and aFresnel lens.
 42. The method of claim 37, wherein said lens comprises aplastic lens.
 43. The method according to claim 37, wherein said lenscomprises a material that transmits radiation with a wavelength betweenapproximately 8 and 14 microns.
 44. The method of claim 43, wherein saidlens comprises a material comprising at least one of Ge, Si, ZnS, CdSand a polyolefin.
 45. The method of claim 27, wherein said thermalenergy detection system consumes a current of less than approximately5.0 mA when operating under vehicle battery power.
 46. The method ofclaim 27, wherein said thermal energy detection system consumes acurrent of less than approximately 1.5 mA when operating under vehiclebattery power.
 47. The method of claim 27, wherein said interiorcompartment comprises a rear-seating area of the vehicle.
 48. The methodof claim 27, wherein said thermal energy detection system is provided asa module.
 49. The method of claim 27, wherein said control circuitrycomprises an application specific integrated circuit.
 50. The method ofclaim 27, wherein said opposed sensing elements are arranged in aparallel opposed connection.
 51. The method of claim 27, wherein saidopposed sensing elements are arranged in a series opposed connection.52. The method of claim 27, wherein said signal generating step will notgenerate a signal for frequencies of change in sensed thermal profilethat are less than approximately 0.5 Hz.
 53. A method of ensuringreliable thermal detection of the presence of a body in a compartment ofa parked motor vehicle comprising the steps of:providing a thermalenergy detection system including a pyroelectric detector, saidpyroelectric detector comprising a first pyroelectric sensing elementand a second pyroelectric sensing element, said first and secondpyroelectric sensing elements arranged in opposed connection, saidthermal energy detection system further comprising control circuitryresponsive to electrical indicatives generated by said opposed first andsecond sensing elements; mounting said thermal energy detection systemeither in a trunk compartment or an interior compartment of the vehicle;monitoring a thermal profile of either said trunk compartment or saidinterior compartment of the vehicle using said thermal energy detectionsystem when the vehicle is parked and operating under vehicle batterypower; sensing a change in the thermal profile due to the presence of amoving human body having a temperature different than the thermalprofile; and generating a signal indicative of the change in the sensedthermal profile in either the trunk compartment or the interiorcompartment,wherein said opposed sensors are arranged in one of aparallel opposed connection and series opposed connection, wherebythermal radiation emitted by said moving human body incident on at leastone of said first pyroelectric sensing element and said secondpyroelectric sensing element generates an output of said thermal energydetection system indicative of presence of a human body in either thetrunk compartment or said interior compartment.
 54. The method accordingto claim 53, wherein the radiation incident on said pyroelectricdetector is filtered to have a wavelength of approximately 8 to 14microns.
 55. The method according to claim 53, wherein said thermalenergy detection system resolves movement of a body at about 37° C.moving at a distance of approximately 1 to 5 meters of said pyroelectricdetector.
 56. The method according to claim 53, wherein said thermalenergy detection system resolves movement of a body at approximately 37°C. moving at a frequency of approximately 5 Hz.
 57. The method accordingto claim 53, wherein the sensing step senses with a sensitivity greaterthan approximately 10⁵ cm Hz/W.
 58. The method according to claim 53,wherein the sensing step senses with a sensitivity greater thanapproximately 10⁶ cm Hz/W.
 59. The method according to claim 53, whereinsaid thermal energy detection system has a power consumption of lessthan approximately 1 Watt when connected to vehicle battery power andwhen the vehicle is in the parked state.
 60. The method according toclaim 53, wherein said thermal energy detection system has a powerconsumption of less than approximately 0.1 Watt when connected tovehicle battery power and when the vehicle is in the parked state. 61.The method according to claim 53, wherein said thermal energy detectionsystem has a power consumption of less than approximately 0.02 Watt whenconnected to vehicle battery power and when the vehicle is in the parkedstate.
 62. The method according to claim 53, furthercomprising:providing a lens, said lens positioned in front of saidpyroelectric detector and focusing incident radiation onto saidpyroelectric detector.
 63. The method according to claim 62, whereinsaid lens comprises a material that transmits radiation with awavelength between approximately 8 and 14 microns.
 64. The methodaccording to claim 63, wherein said lens blocks radiation having awavelength of approximately 0.3 to 3 microns.
 65. The method of claim63, wherein said lens comprises a material comprising at least one ofGe, Si, ZnS, CdS and a polyolefin.
 66. The method of claim 62, whereinsaid lens comprises a polyolefin material.
 67. The method of claim 62,wherein said lens comprises a material comprising at least one of apolypropylene, a polyethylene and a polymethylpentene material, or acopolymer thereof.
 68. The method of claim 62, wherein said lenscomprises at least one of a fish eye lens, a diffractive optic lens, awide angle lens and a Fresnel lens.
 69. The method of claim 62, whereinsaid lens comprises a plastic lens.
 70. The method of claim 53, whereinsaid thermal energy detection system consumes a current of less thanapproximately 5.0 mA when operating under vehicle battery power.
 71. Themethod of claim 53, wherein said thermal energy detection systemconsumes a current of less than approximately 1.5 mA when operatingunder vehicle battery power.
 72. The method of claim 53, wherein saidinterior compartment comprises a rear-seating area of the vehicle. 73.The method of claim 53, wherein said thermal energy detection system isprovided as a module.
 74. The method of claim 53, wherein said controlcircuitry comprises an application specific integrated circuit.
 75. Themethod of claim 53, wherein said opposed sensing elements are arrangedin a parallel opposed connection.
 76. The method of claim 53, whereinsaid opposed sensing elements are arranged in a series opposedconnection.
 77. The method of claim 53, wherein said signal generatingstep will not generate a signal for frequencies of change in sensedthermal profile that are less than approximately 0.5 Hz.
 78. A method ofensuring reliable thermal detection of the presence of a body in acompartment of a parked motor vehicle comprising the steps of:providinga thermal energy detection system including a pyroelectric detector,said pyroelectric detector comprising a first pyroelectric sensingelement and a second pyroelectric sensing element, said first and secondpyroelectric sensing elements arranged in opposed connection, saidthermal energy detection system further comprising control circuitryresponsive to electrical indicatives generated by said opposed first andsecond sensing elements; mounting said thermal energy detection systemeither in a trunk compartment or an interior compartment of the vehicle;monitoring a thermal profile of either said trunk compartment or saidinterior compartment of the vehicle using said thermal energy detectionsystem when the vehicle is parked and operating under vehicle batterypower; sensing a change in the thermal profile due to the presence of amoving human body having a temperature different than the thermalprofile; and generating a signal indicative of the change in the sensedthermal profile in either the trunk compartment or the interiorcompartment; wherein said thermal energy detection system consumes acurrent of less than 5.0 mA when operating under vehicle battery power,whereby thermal radiation emitted by said moving human body incident onat least one of said first pyroelectric sensing element and said secondpyroelectric sensing element generates an output of said thermal energydetection system indicative of presence of a human body in either thetrunk compartment or said interior compartment.
 79. The method accordingto claim 78, wherein the radiation incident on said pyroelectricdetector is filtered to have a wavelength of approximately 8 to 14microns.
 80. The method according to claim 78, wherein said thermalenergy detection system resolves movement of a body at about 37° C.moving at a distance of approximately 1 to 5 meters of said pyroelectricdetector.
 81. The method according to claim 78, wherein said thermalenergy detection system resolves movement of a body at approximately 37°C. moving at a frequency of approximately 5 Hz.
 82. The method accordingto claim 78, wherein the sensing step senses with a sensitivity greaterthan approximately 10⁵ cm Hz/W.
 83. The method according to claim 78,wherein the sensing step senses with a sensitivity greater thanapproximately 10⁶ cm Hz/W.
 84. The method according to claim 78, whereinsaid thermal energy detection system has a power consumption of lessthan approximately 1 Watt when connected to vehicle battery power andwhen the vehicle is in the parked state.
 85. The method according toclaim 78, wherein said thermal energy detection system has a powerconsumption of less than approximately 0.1 Watt when connected tovehicle battery power and when the vehicle is in the parked state. 86.The method according to claim 78, wherein said thermal energy detectionsystem has a power consumption of less than approximately 0.02 Watt whenconnected to vehicle battery power and when the vehicle is in the parkedstate.
 87. The method according to claim 78, furthercomprising:providing a lens, said lens positioned in front of saidpyroelectric detector and focusing incident radiation onto saidpyroelectric detector.
 88. The method according to claim 78, whereinsaid lens comprises a material that transmits radiation with awavelength between approximately 8 and 14 microns.
 89. The methodaccording to claim 78 wherein said lens blocks radiation having awavelength of approximately 0.3 to 3 microns.
 90. The method of claim 78wherein said lens comprises a material comprising at least one of Ge,Si, ZnS, CdS and a polyolefin.
 91. The method of claim 78, wherein saidlens comprises a polyolefin material.
 92. The method of claim 78,wherein said lens comprises a material comprising at least one of apolypropylene, a polyethylene and a polymethylpentene material, or acopolymer thereof.
 93. The method of claim 78, wherein said lenscomprises at least one of a fish eye lens, a diffractive optic lens, awide angle lens and a Fresnel lens.
 94. The method of claim 78, whereinsaid thermal energy detection system consumes a current of less thanapproximately 1.5 mA when operating under vehicle battery power.
 95. Themethod of claim 78, wherein said interior compartment comprises arear-seating area of the vehicle.
 96. The method of claim 78, whereinsaid thermal energy detection system is provided as a module.
 97. Themethod of claim 78, wherein said lens comprises a plastic lens.
 98. Themethod of claim 78, wherein said control circuitry comprises anapplication specific integrated circuit.
 99. The method of claim 78,wherein said opposed sensing elements are arranged in a parallel opposedconnection.
 100. The method of claim 78, wherein said opposed sensingelements are arranged in a series opposed connection.
 101. The method ofclaim 78, wherein said signal generating step will not generate a signalfor frequencies of change in sensed thermal profile that are less thanapproximately 0.5 Hz.